Inertia armed fuze



y 1968 s. J. KENT INERTIA ARMED FUZE 2 Sheets-Sheet 1 Filed May 4, 1967 ON N mm vm INVENTOR STANLEY J. KENT BY m, 1. 5 5 1 ATTORNEY5 July 2, 1968 5. J. KENT INERTIA ARMED FUZE 2 Sheets-Sheet 2 Filed May 4, 1967 8 JL m VI E Em N on mm m m f r W8 A -m P mm W United States Patent 3,390,637 INERTIA ARMED FUZE Stanley J. Kent, Philadelphia, Pa., assignor to the United States of America as represented by the Secretary of the Army Fiied May 4, 1967, Ser. No. 637,048 3 Claims. (Cl. 102-78) ABSTRACT OF THE DISCLOSURE A fuze having a tubular body with a firing pin at the forward end and a charge at the rearward end. A sliding ignition element, in the tubular body, has an hour glass shaped axial cavity therein which has a firing pin in its forward portion, a detonating charge in its rearward portion. An expandable lock ring is provided in a groove encircling the ignition element with a spring washer wedging the ignition element against the ring to prevent looseness. When setback occurs the lock washer will be compressed by a shoulder of the ignition element thereby transferring the setback force to the lock ring, forcing it to cam out of the groove, to rest against the inside of the expanded ring, until impact.

The inventon relates to a fuze and more particularly concerns an inertia-type fuze incorporating a novel setback mechanism, the resultant fuze having features permitting its safe handling.

It is a precautionary requirement in handling artillery ammunition fuzes that after its assembly to a projectile, the assembly may be dropped, rolled or otherwise roughly handled without the initiation of the firing train. It is also essential, that when the projectile is fired, the explosive train will not function until the projectile has traveled a sufficiently safe distance from the gun so as not to injure the gun crew.

-In the past, it was common practim to have such arming mechanisms depend for their action upon the operation of a built-in clock-like gear train mechanism driven by spring action, or by centrifugal force generated as a result of projectile spin. In many cases, spring action or centrifugal force relied, in turn, upon one or more shear pins or upon bore riding pins.

Gear train mechanisms of the size used in arming devices, whether driven by spring action or actuated by centrifugal force, were inherently delicate and susceptible to malfunctioning. In addition, they were expensive to manufacture and assemble and, when completed, required careful handling to preserve their operability and thus placing an unnecessary task upon those responsible for their handling. It has been often found that a gear train mechanism would fail to operate when subjected to severe shock created at the time of firing the missile.

The use of one or more shear pins, whose failure at the time of firing allowed a gear train mechanism to begin its cycle of operation, also has left much to be desired. These pins have sometimes failed to shear off, or have been found to shear off in such a way as to prohibit or retard proper operation of the gear train mechanism with attendant ineffective results.

In the past bore riding pins used in arming mechanisms etfetced release of the mechanisms gear train by moving radially outward as soon as the missile passed from the gun barrel. No attempt, however, was made to limit the outward movement of these pins, and consequently, they flew off into space in random paths, and presented a hazard to the personnel and equipment in the vicinity.

It is therefore, an object of the present invention to provide a fuze having a novel set back mechanism which prevents the fuze from arming until it has traveled a suflicient distance from the gun.

Another object is the provision of an impact detonating fuze which does not require collapse of the missile housing to displace the firing pin for contact of the primer element.

Still another object is to provide an impact detonating fuze that will function in a soft impact media.

A further object is the provision of an impact detonating fuze that will not explode by abusive handling.

The above objects, as well as others, together with the benefits and advantages of the invention will be apparent upon reference to the detailed description set forth below, particularly when taken in conjunction with the drawings annexed hereto in which:

FIG. 1 illustrates a plan view in section, of the invention in its initial safe position;

FIG. 2 shows a sectional view of the invention in its setback positon;

FIG. 3 shows a sectional view of the invention in its impact position.

Referring now to the drawings, fuze 10 which can be utilized in an artillery shell or other impact detonating type of projectile, has a cartridge or ignition element 12, which is locked in a cylindrical body or main tube 14 of fuze 10 by means of a lock ring 16, which is installed in a groove 18. A spring washer 20 is used to take up looseness by wedging inclined surface 22 of the cartridge 12 against the inside surface of the locking ring 16.

When setback occurs, as seen in FIG. 2, the cartridge shoulder 24 (FIG. 1) compresses spring washer 20 thereby transferring the setback force to the lock ring 16 forcing it to cam out of the groove 18 and into space 26 presented by the advance of the cartridge 12. The washer carries the lock ring 16 to notch 28 and then rests against the inside of the expanded ring 16 until impact occurs.

Upon impact, as seen in FIG. 3, the cartridge 12 travels in the direction of the fixed firing pin 30, having a nipple 32, which makes forced contact with the cartridge primer 34 (see FIG. 1). The location of the cartridge 12, after unlocking by the setback force, is fixed by having the conical locking surface 42 terminate with a diameter greater than the inside diameter of the lock ring 16 when in the notch 28. To contact the firing pin 30, the cartridge must forcibly expand the lock ring 16 and pass through. Relief of the interference is provided by having a reduced cartridge diameter 44 at the end of the conical area.

The cartridge primer 34 which could be, for example, lead azide, ignites a detonator 36, which could be for example, lead azide, PETN, or the like; the detonator 36 is encased in an ignitor tube 38 which in turn ignites a booster charge 40, containing for example, TNT, R-DX, or the like. The explosion of the booster charge 40 ignites the main charge, not shown, of the artillery shell, not shown.

This novel fuze is functional in a soft impact media and therefore does not require the collapse of the housing to displace the firing pin for contact of the primer element. This is so because once the tremendous set back occurs the fuze is free to detonate at any time that said set back force is released, i.e., upon hard impact, soft impact or just a sudden reduction of speed. It is essential that the cartridge occupy the position where it has sufficient kinetic energy to ignite the cartridge. This functioning position provides necessary traveling distance between the firing pin and the cartridge.

It should be noted at this time that the fuze could be mounted in any position, e.g., in the base, in the artillery shell and will still operate successfully.

Obviously many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood, that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

I claim:

1. A fuze for attachment to a projectile comprising:

a tubular body having a firing pin secured at the torward end thereof and a booster charge secured at the rearward end thereof,

an ignition element slidably secured in said body having an axial cavity therethrough.

a cartridge primer secured in the forward portion of said axial cavity,

a detonating charge secured in the rearward portion of said cavity,

means encircling said ignition element at the rorward end thereof for releasably holding said element secure in said body,

means adjacent said encircling means to take up looseness between said element and said body,

means carried by said ignition element for effecting release of said element during set back,

said encircling means including an expandable lock ring installed in a groove encircling said ignition eiement at the. forward end thereof, and

4 said ndiacent means including a spring washer which ts edges a conical surface of said element against lock l'lng thereby taking up looseness. it. A fuze or the type described in claim 1 including a notch defined by the inner surface of said tubular body, said notch acting as a resting place for said lock ring during Set back.

ii. A fuze of the type described in claim 1 wherein said third mentioned means constitutes a shoulder portion on said ignition element.

\References Cited UNITED STATES PATENTS b97974 /1902 Broderick 102-78 1330.933 M1917 Simpson 10278 l1,280,52l iO/l918 Morn 10278 Iii,289,588 12/1966 Hitchens et a1. 102-78 X BENJAMIN A. BORCHELT, Primary Examiner.

iii, H. SLANZMAN, Assistant Examiner. 

